A standard myotomy and myectomy has been performed for relief of left ventricular outflow tract obstruction secondary to asymetric septal hypertrophy (ASH) in 410 patients. Fifty-eight patients have been operated upon and an attempt has been made to tailor the operative approach depending upon septal thickness, distribution, level of systolic anterior motion contact of septum and concomitant coronary artery disease. Intraoperative 2D and M-mode echos have been performed on a number of these patients providing precise data utilized intraoperatively. Patients with concomitant CAD represent a higher risk for VSD creation which may be avoided by a modified left ventricular myotomy and myectomy or mitral valve replacement. Hemodynamic data are presented based on preoperative resting gradients 0-50 mm Hg (n = 13) and greater than 50 mm Hg (n = 45). Postoperative hemodynamic studies reveal good relief of resting gradient in most patients but significant provocable gradients remain in some patients, especially in those with preoperative resting gradients greater than 50 mm Hg. Medical therapy is continued in patients with significant provocable gradients following operative palliation.